Dinosaur species have made the Arctic their permanent home and probably developed techniques like hibernation or feathers to survive the cold, according to a new study.
The paper, published this week in the journal Current Biology, is the result of more than a decade of fossil excavations and undermines the idea that these reptiles lived only in milder latitudes.
“Some of the new sites discovered in recent years have revealed some amazing things, namely the bones and teeth of baby dinosaurs,” senior study author Patrick Druckenmiller of the University of Alaska told AFP.
“It’s amazing, because it shows that these dinosaurs not only lived in the Arctic, but were able to breed there as well,” he continued.
Scientists first discovered dinosaur remains in 1950 in a region that had long been considered too hostile to have reptiles.
Two competing hypotheses were then formulated: either the dinosaurs lived there permanently, or they migrated to the Arctic and Antarctic to make seasonal use of available resources and perhaps to breed there.
This new study is the first to show evidence that at least seven dinosaur species could have bred at these extremely high latitudes – in this case the Prince Creek Formation in Alaska, between 80 and 85 degrees north latitude, which originates from the Upper Cretaceous.
Discovered species include hadrosaurids, called dinosaurs with ducks, horned dinosaurs like ceratopsies, and carnivores like tyrannosaurs.
A team of researchers found small teeth and bones, some of which are only a few millimeters in diameter, belonging to dinosaurs that had just hatched or died just before.
“They have a certain kind of texture on the surface and they’re very specific – they’re very vascular, and the bones grow very fast, a lot of blood vessels go through them,” Patrick Druckenmiller explained.
Unlike other mammals like the caribou, whose offspring can travel long distances almost immediately after birth, even the largest dinosaurs have given birth to cubs that would not be able to cope with migrations of several thousand kilometers.
– Down jacket with feathers –
“We think of dinosaurs in tropical environments like this, but the whole Earth wasn’t like that,” Patrick Druckenmiller recalls.
Then the Arctic was warmer than it is today, but the conditions were still very demanding.
The annual temperature was around 6 ° C, but much lower temperatures were on the agenda, with snowfall, during the winter months.
This area was probably covered with conifers or ferns.
“We now know that most of the carnivorous dinosaurs that were there probably had feathers,” Patrick Druckenmiller said. “You can think of it as their own down jacket, which will help them survive the winter.”
As for smaller herbivores, researchers believe they would bury themselves underground and hibernate.
And the older ones, with more fat stores, relied on poorer and lower-quality crusts to survive the winter.
On the other hand, the fact that dinosaurs resided in the Arctic throughout the year is an additional clue to the idea that dinosaurs were warm-blooded animals, as other recent studies suggest. They would then represent the point of evolution between cold-blooded reptiles and warm-blooded birds.
Their ability to survive the Arctic winter “is by far the most convincing evidence” that they can be added to the list of species capable of thermoregulation, concluded Gregory Erickson of Florida State University and co-author of the study.